Mine roof supporting structure



March 15, 1966 M. MERIAUX ETAL MINE ROOF SUPPORTING STRUCTURE 3Sheets-Sheet 1 Filed July 20, 1962 M. MERIAUX ETAL 3,240,021

mm ROOF surronwme STRUCTURE 3 Sheets-Sheet 2 9 N u A mi; i

March 15, 1966 Filed July 20, 1962 MINE ROOF SUPPORTING STRUCTURE FiledJuly 20, 1962 3 Sheets-Sheet 3 Fig.4

United States Patent 3,24%,ti21 MHNE RUUF SUPPQRTlNG STRUQTURE MichelMeriaux and Michel habiachoflombier, Witteh sheim, France, assignors toMines Domaniales do Potasse dAlsace, Mulhouse, Ham-Rhine, France, aFrench society Fitted .luiy 20, 1962, Ser. No. 211,344 Claims priority,application France, July 22, 1961, 868,738 3 Claims. (Cl. 6145) Theconventional form of support in mine roof supporting structuresessentially comprises, at the edge of the blasting region, a very highlyresistant supporting line made up of piles or props, and usually, anauxiliary support in the working passage, usually made up of props withor without extensions.

In mechanised workings, in which a working passage is required to bekept clear as possible, auxiliary support for overhang by extensions onprops or piles is being adopted to a greater and greater extent, sinceit makes it possible to have a free front line of props along which acutting machine, such as a plane or undercutter, can run without anytrouble.

However, a large labour force is required for using a system ofmechanical extensions on props or piles, since extremely large tonnagesof equipment have to be handled each time the supporting system ismoved.

Systematic use of hydraulic control means in working faces having movingsupporting systems has enabled the operation of placing the extensionsin position to be fully mechanised, with all the desired flexibility andconvenience in use.

To this end, movable supporting elements in present day embodiments arevery often equipped with extensions of different types, intended tosupport the roof above the working passage; these extensions are usuallyclamped against the roof by a mechanical system; sometimes they are ofthe hydraulic-lift type.

However, there is very often only a little free height remaining betweenthe cutting machines and the roof; the extensions then become a greatnuisance, and have to be dismantled for the cutting machine to pass.Even if the cutting machine can run below the extensions under normalconditions, the latter abut against the machine as soon as the roofsubsides abnormally, and have to be dismantled or folded back.

The present invention seeks to allow these disadvantages to be overcome,and in accordance with the invention, a mine roof supporting structurecomprises an extension which is adapted to be slidably mounted in arecess in a roof supporting member for movement between a retractedposition and an extended position in which it projects forwardly fromthe said member, and a hydraulic clamping device which is operative toforce the extension, in its extended position, against a mine roof.

Preferably, a second extension is provided which is housed in the firstextension, and is movable between a retracted position and an extendedposition, and can be clamped in its extended position between the firstextension and the mine roof.

Such a structure can be so arranged that, when the said extensions arefully extended, they can immediately sup port the roof which isuncovered after the cutting machine has passed; in addition, theextensions may be capable of being fully retracted into the cover of themain supporting element should the roof subside or also should thecutting machines be particularly bulky, and this possibility enables theworking passage to be completely cleared for the said machines to pass.Moreover,

the extension system may be retracted at the last moment, that is to sayeven if the front part of the cutting machine is already engaged underthe said extensions; in addition to this great flexibility in useconferred on it by its mechanical design, this system of extensions isdesigned to be hydraulically clamped against the roof, that is to say itexhibits all the advantages of the hydraulic supporting system.

Features and advantages of the invention will become clear from thefollowing description of two preferred forms thereof which areillustrated in the accompanying drawings.

FIGURE 1 is a sectional elevation of a supporting structure inaccordance. Wtih the invention;

FIGURE 2 is a part-sectioned elevation, similar to FIGURE 1, showingsome parts in different relative positions;

FIGURE 3 is an elevation similar to FIGURE 1, showing parts in otherdifferent relative positions; and

FIGURE 4 is an elevation of a variant of embodiment.

With particular reference to FIGURE 1 of the drawing, the supportingstructure comprises a first extension l which can retract fully into thecover 2 of a main roof supporting element, and a second extension 3which can be fully retracted into the extension 1. However, the secondextension 3 need not be provided unless there is a large degree ofoverhang to be supported; if less protection is suflicient, thestructure need comprise only the single extension l.

The first extension it consists of a steel box-girder element, of aprofile which enables heavy stresses to be withstood, while leaving theinternal space la required for the second extension 3 to be able to befully accommodated therein. At its forward end, the first extension llcomprises bearing portion 1b which is forced against the roof whenclamping takes place, and, if required lugs (not illustrated), intendedto facilitate extending and retracting movements of the said extension.At its rear end the extension 1 is formed with a stroke-limitingabutment 1c which can cooperate with a cross-member 2a mounted in thecover 2 in order to prevent the extension from emerging from the saidcover when not required to do so. If required, this abutment may be usedto guide the extension 1 inside the recess 2b in the cover 2. In itslower face, the extension 1 has a spherical cavity 1d intended toreceive the head 4a of a hydraulic jack 4 which will be described later.

In the retracted or non-operative position, only the handling lugs ofthe extension ll protrude from the cover 2; in the extended or Workingposition, the extension comes to bear under the action of the jack 4against the abutment 1c and against the head 4:: of the jack, while thebearing portion 1b comes into contact with the roof 5 of the workingpassage (see FIGURE 2). The stroke of the stern of the jack 4 and thedimensions of the extension 1 are so calculated that this contact can bemade with large amounts of inclination between the extension and thecover 2: for example, angles of 7 to 8 may easily be obtained forextension lengths of 800 to 1000 mm. The aperture in the cover 2 mayalso be made of flared shape in order to give increased possibilities ofclearance to the extension l, and to enable the system of extensions tobe adapted to very undulating roofs (see positions A, B, C, FIGURE 2).

The second extension 3 is intended to lengthen the extension 1 up to theface of the workings in order to support the new roof uncovered by thecutting machine, just after the latter has passed. In view of the factthat the stresses to be taken into consideration are much less heavy inthe case of the extension 3, the latter may be a single strip of springsteel, or ordinary steel, according to the roofs encountered. Ifcircumstances require, it may also be a profiled member of any shape.This secnd extension 3 retracts fully into the internal space 1a of theextension 1; it is furthermore fitted with a strokelimiting abutment 3awhich can cooperate with a shoulder 16 on the upper wall of the recess1a in order to prevent the extension 3 from emerging completely from itsrecess. In the telescoped or retracted position, this extension 3 may beclamped against the roof, without any need to touch the extension 1, byvirtue of an auxiliary clamping system using a wedge 6. This clampingdevice enables the extension 3 to be correctly clamped against the roof5, even if the latter comprises undulations or irregularities (seeFIGURE 3).

This make it possible to embody a system of extensions enabling supportto be provided, for example, for a load of 500 kg., which is assumed tobe concentrated at the end of the second extension 3, in addition to aload of one ton at the end of the first extension 1 on the carrier plate1b.

The operation of sliding the extensions is particularly easy, sincethese pieces move in a horizontal plane.

The hydraulic clamping device is intended on the one hand to clamp thewhole telescopic unit against the roof, and on the other hand to controllowering of the roof by offering a definite resistance. It takes theform of a hydraulic jack mounted on a bracket 7 fast with the cover 2 ofthe supporting element.

The jack 4 may be a single-acting hydraulic jack, the weight of theextensions as a whole being quite sufficient to force the ram into thecylinder when the jack is re lieved of pressure. Its stroke must besutficient to give clearance for the higher extensions (positions A, B,C, FIGURE 2), and the force which it develops is clearly a function ofthe loads which it is desired to support at the end of the extensions 1and 3, and must consequently be adapted to the resistance to bendingexhibited by the said extensions. For example, for the loads envisagedabove on the extensions 1 and 3, a force of 8 to 9 tons for the jack 4is very suitable. The jack may be fed by a single conduit which givesboth feed and return, inlet (when the feed pump is running) or exhaust(when the pump is stopped) being via the same Valve (needle-tap, poppetvalve or any other similar device).

In order to prevent undue bending stresses to be set up in theextensions due to collapsing of the mine roof, there is provided asafety valve (not shown) for relieving the pressure in the jack wherebyto allow the jack to telescope under a predetermined mine roof pressure.The pressure required for clamping purposes must be very close to thepressure at which the valve will open in order to limit as far aspossible the effects due to elastic deforma tion of the extensions. Forexample, if clamping is to take place at 200 kg./cm. the safety valvemay be set for a pressure of 250 kg./cm.

The safety valve may be mounted on the jack unit itself, and may exhaustto atmosphere. In view of the small cross-section of the jack, thevolume of liquid to be discharged if sliding occurs will remainpractically negligible.

The auxiliary clamping device 6 enables the extension 3 to be locked orunlocked independently of the extension 1.

This device is a simple wedge which can be attached by a small chain tothe end of the extension 1. For clamping purposes, this wedge isinserted and clamped under the extension 3 at the entrance to the recess1a; the extension 3 is then forced against the roof 5, and bears againstthe stroke-limiting abutment 3a and the wedge 6.

The system of extensions is furthermore so calculated that if a load isapplied at any point on one of the extensions 1 or 3 when they are fullyextended the jack 4 will collapse before the elastic limit of one of thesaid extensions is reached.

The lengths of the two extensions 1 and 3, their profiles, theirmechanical resistances, and the force developed by the jack 4 and itsstroke are clearly a function of the local conditions of the roof, thewidth of the working passage, and the depth of cut of the cuttingmachine.

For optimum operation, the various features of the system of extensionsmust therefore be adapted to the characteristics of the workings; theextensions are made and designed to work normally in the fully extendedstate, and they must be calculated for these conditions, which are themost unfavourable.

However, it must be noted that each of the extensions 1, 3 may beclamped against the roof in any position intermediate its retracted andfully extended positions, which clearly gives the system very greatflexibility in use by allowing the bearing portion of the extension 1 orof the extension 3 to be placed at a carefully chosen point. For exampleit may be desired to support a particular portion of the roof which iscracked or fractured or is otherwise of doubtful strength. Similarly, ifthe working passage is abnormally contracted one or other of the twoextensions, or both, may be used partially or fully extended.

The following examples illustrate the use of the above describedstructure in various circumstances.

(1) Before the cutting machine arrives, the first extension 1 (FIGURE 2)is fully extended from the cover 2 of the main supporting element; theextension 1 is clamped against the roof 5 by the jack 4; with the secondextension 3 normally in its retracted position in the extension 1, thewedge 6 being simply lodged under the extension 3 at the entrance to therecess 1a. If roof conditions are difiicult, the extension 3 may beextended from the extension 1 as far as the face of the workings, thusgiving protection to the whole working passage.

(2) As the cutting machine approaches, two cases are then possible:

(a) If the roof is normal, and the cutting machine is not too bulky asregards height, so that there is a clear ance of more {than about tencentimetres between the roof and the said machine; in this case, theextension 1 may be left in place, and will continue to support the roofabove the machine all the time it is moving. Immediately after themachine has passed, the extension 3 is fully extended from the extension1 and clamped against the roof by its wedge 6; the roof which has justbeen uncovered is therefore immediately supported.

(b) If the roof has subsided abnormally, in consequence of a blastingoperation, for example, or even if, under normal conditions, the cuttingmachine does not leave sutficient clearance between itself and the roof,the extension 1 cannot be kept above the machine while the latter ismoving.

In these circumstances, the extensions 1 is retracted into the cover 2at the last moment. The jack 4 is exhausted and the extension 1 is freedand can thus be retracted into the cover 2, the extension 3 stillremaining inside the extension 1. This operaion may be carried out inall cases at the very last moment, even if the front part of the machineis already engaged under the extension, and this is a considerableadvantage with respect to known pivoting or demountahle extensions, theremoval of which involves insoluble problems once the machine isengaged. If the roof is very unsafe after the extension 1 has been fullyretracted and re-clamped by restoring pressure to the jack 4, theextension 3, which is much less thick than the extension 1, may incertain cases be extended and re-clamped against the roof; thisadditional protection may be advantageous with very difficult roofs.

After the cutting machine has passed, the jack 4- is unclamped, theextension 1 is brought fully extended from the cover 2 again, theextension 3 is extracted from the extension 1, the wedge 6 is placed inposition, and the whole is re-clamped against the roof by the jack 4; asin the foregoing case, the roof which has been uncovered is supportedimmediately the machine has passed.

(3) To return the cutting machine, in the case of cutting machinesworking in a single direction along the front, the machine will in mostcases be able to pass below the fully spread out system of telescopicextensions without any operation having to be carried out; as a generalrule, in fact, the cutting machine is considerably lower in the returnposition than in the cutting position.

If this were not the case, or if the roof had subsided considerably inconsequence of a blasting operation, the same operations as thosedescribed in Example 2 above could be carried out upon return.

(4) Upon moving the supporting system at the instant when the pile ismoved, the cover 2 is disengaged from the roof; the whole telescopicunit is therefore automatically unlocked. The only additional operationconsists in returning the extension 3 into the extension 1 (fully orotherwise), after the cover has been disengaged. The cover 2 being againclamped against the roof in its new position, all that remains is torestore pressure to the jack 4 of the telescopic unit.

Since the telescopic device is intended most of the time to complete amoving hydraulic supporting system, suitable connection of the hydraulicmeans can automatically restore pressure to the jack 4 at the instantwhen the pile is moved; the telescopic unit will be automaticallyre-clamped at the instant when the pile is re-locked, excess liquid frominside the jack 4 being discharged via the safety valve, operation ofthe device being thus further simplified.

In the second embodiment illustrated in FIGURE 4 of the drawing, thejack 4', instead of being mounted on a bracket fast with the cover 2, isfixed at the end of the first extension 1, and moves in unit with thesaid extension. This jack may be fed by a flexible pipe 472 which isfitted inside the cover 2 in order not to hinder movement of the systemof extensions.

In addition, a bearing plate is pivoted at the entrance of the recess2b. In the telescoped or retracted position, the jack 4' acts verticallyupwardly on the upper wall of the recess 2b to bring the extension 1 tobear both against the piece 20 and the head 4a of the said jack. Thissystem of extensions is used in the same way as the system of extensionsdescribed above.

The advantage of this variant is that it is less bulky, enabling it tobe used in shallow seams.

The advantages exhibited by the structure described above are variouswhen the roof is used for the support of unsafe roofs.

The structure primarily is intended for incorporation in any hydraulicsupporting system, in particular a moving supporting system; however, itmay be adapted to any kind of supporting system comprising a cover whichwill enable the extension 1 to be accommodated in the retractedposition.

Because it enables practically any working passage to be covered, andalso allows for strict control of lowering of the roof, the structuredescribed above gives virtually complete safety in working faces inreturn for very simple operations. Its flexibility and convenience inuse are its essential qualities: it makes it possble to uncover only thevery minimum required for the cutting machine to pass, which is anindispensable condition in the case of poor roofs.

Its operation is particularly simple when it is used on a movingsupporting system, and when it is itself controlled by a hydraulic jack.

Various modifications in the structure described above can of course bemade within the scope of the invention; for example the wedges 6 couldbe replaced by any equivalent clamping means.

We claim:

1. In a mine roof supporting structure, the combination comprising amine roof supporting member having a hollow interior defining a recess,an extension member slidably disposed in said recess in a telescopingarrangement, said extension member being movable from a retractedposition in the recess to an extended position relative to the recess,one end of said extension member remaining Within said recess, a bearingmember positioned within said recess adjacent one end of said supportingmember, said bearing member adapted to engage said extension memberintermediate the ends thereof to thereby provide a fulcrum for theextension member when at the extended position, hydraulic clamping meanssecured to said extension member in proximity to said one end thereof,said hydraulic clamping means being carried as a. unit by the extensionmember and movable therewith, said hydraulic clamping means including ahydraulic jack having a ram element, said ram element being movable intoengagement with the interior of said supporting member, whereby saidextension member is pivoted about the bearing member such that said oneend of said extension member moves in one direction and the opposite endof said extension member is moved in the opposite direction and forcedagainst a mine roof.

2. The combination as recited in claim 1, wherein said extension memberis hollow and a second extension member is slidably disposed therein.

3. The combination as recited in claim 2 wherein wedging means isoperatively disposed between said extension member and said secondextension member.

References Cited by the Examiner UNITED STATES PATENTS 3,127,748 4/1964Cooke 61-45.2

FOREIGN PATENTS 1,192,849 4/1959 France.

1,245,142 9/1960 France.

1,077,618 3/1960 I Germany.

823,586 11/1959 Great Britain.

CHARLES E. OCONNELL, Primary Examiner.

JACOB L. NACKENOFF, EARL I. WITMER,

Examiners.

1. IN A MINE ROOF SUPPORTING STRUCTURE, THE COMBINATION COMPRISING AMINE ROOF SUPPORTING MEMBER HAVING A HOLLOW INTERIOR DEFINING A RECESS,AN EXTENSION MEMBER SLIDABLY DISPOSED IN SAID RECESS IN TELESCOPINGARRANGEMENT, SAID EXTENSION MEMBER BEING MOVABLE FROM A RETRACTEDPOSITION IN THE RECESS TO AN EXTENDED POSITION RELATIVE TO THE RECESS,ONE END OF SAID EXTENSION MEMBER REMAINING WITHIN SAID RECESS, A BEARINGMEMBER POSITIONED WITHIN SAID RECESS ADJACENT ONE END OF SAID SUPPORTINGMEMBER, SAID BEARING MEMBER ADAPTED TO ENGAGE SAID EXTENSION MEMBERINTERMEDIATE THE ENDS THEREOF TO THEREBY PROVIDE A FULCRUM FOR THEEXTENSION MEMBER WHEN AT THE EXTENDED POSITION, HYDRAULIC CLAMPING MEANSSECURED TO SAID EXTENSION MEMBER IN PROXIMITY TO SAID ONE END THEREOF,SAID HYDRAULIC CLAMPING MEANS BEING CARRIED AS A UNIT BY THE EXTENSIONMEMBER AND MOVABLE THEREWITH, SAID HYDRAULIC CLAMPING MEANS INCLUDING AHYDRAULIC JACK HAVING A RAM ELEMENT, SAID RAM ELEMENT BEING MOVABLE INTOENGAGEMENT WITH THE INTERIOR OF SAID SUPPORTING MEMBER, WHEREBY SAIDEXTENSION MEMBER IS PIVOTED ABOUT THE BEARING MEMBER SUCH THAT SAID ONEEND OF SAID EXTENSION MEMBER MOVES IN ONE DIRECTION AND THE OPPOSITE ENDOF SAID EXTENSION MEMBER IS MOVED IN THE OPPOSITE DIRECTION AND FORCEDAGAINST A MINE ROOF.